1. Field of the Invention
The present invention relates to cementing generally, and more particularly, to cement compositions which set into resilient high strength masses.
2. Description of the Prior Art
Hydraulic cement compositions are commonly utilized in forming structures above and below ground. In forming such structures, a hydraulic cement composition is pumped into a form or other location to be cemented and allowed to set therein. Generally, the set cement compositions must have high shear bond strength to avoid bond failure.
In the construction and repair of wells such as oil and gas wells, hydraulic cement compositions are pumped into locations therein to be cemented and allowed to set. In primary well cementing, a hydraulic cement composition is pumped into the annular space between the walls of the well bore and the exterior surfaces of a pipe string disposed therein. The cement composition is permitted to set in the annular space thereby forming an annular sheath of hardened substantially impermeable cement therein. The cement sheath physically supports and positions the pipe string in the well bore and bonds the exterior surfaces of the pipe string to the walls of the well bore whereby the undesirable migration of fluids between zones or formations penetrated by the well bore is prevented.
The cement sheath in the annulus between a pipe string and the walls of a well bore often fails due to pipe movements which cause shear stresses to be exerted on the set cement. Such stress conditions are commonly the result of relatively high fluid pressures and/or temperatures inside the cemented pipe string during testing, perforating, fluid injection or fluid production. The high internal pipe pressure and/or temperature can result in the expansion of the pipe string, both radially and longitudinally, which places stresses on the cement sheath causing the cement bond between the exterior surfaces of the pipe or the well bore walls, or both, to fail which allows leakage of formation fluids, etc.
Thus, there are needs for improved cement compositions and methods whereby after setting, the cement compositions form solid masses which have high bond strengths sufficient to withstand stresses without failure.